strange pattern on the left side in code editor

[tjareson]

Hello,
I'm a bit lost as I don't even know what to search for. I've just installed codeblocks 20.3 on Linux Mint 21.1 Cinnamon.
An I see a black "pattern" in the code editor on the left side where the line numbers are. (see attached picture)

Does anyone know what that is?

[tjareson]

Solved - it just disappeared after reboot.